2002 F250SD transmission cooler lines

I've searched here and found answers of both 5/16" and 3/8", so I'm curious if anyone knows for sure what size the transmission cooler pipes coming off the trans are on a 2002 F250 with 4R100? Also, are the flares standard double flare or something special? I am planning to replace my corroded lines but don't want to risk breaking the heavily corroded fittings checking out the flares. Thank you for any help.

If you are replacing with stainless tubing then standard flare will be your only option anyway. I always use stainless tubing when given the opportunity, it's much more durable than the original mild steel stuff.

Shake and Bake, the flare I must make is dependent on the fittings on the car. It is extremely likely they are SAE 45* double flare fittings, but if anyone could let me know for sure I'd like to ensure I've got a compatible flaring tool and parts handy before tearing out these very rusted lines.

Shake and Bake, the flare I must make is dependent on the fittings on the car. It is extremely likely they are SAE 45* double flare fittings, but if anyone could let me know for sure I'd like to ensure I've got a compatible flaring tool and parts handy before tearing out these very rusted lines.

In case you are interested...
Replacement lines are available via OEM or aftermarket. Dorman makes them in stainless or mild steel.

If you already have all the necessary flaring tools then it's probably easier and quicker to make your own. I do it both ways. Some stuff is just easier to order pre-made while other stuff comes out better by doing it yourself. You might try and visit the dealer and have them pull the part so you can inspect the flare and then you'll know for sure.

In case you are interested...
Replacement lines are available via OEM or aftermarket. Dorman makes them in stainless or mild steel.

If you already have all the necessary flaring tools then it's probably easier and quicker to make your own. I do it both ways. Some stuff is just easier to order pre-made while other stuff comes out better by doing it yourself. You might try and visit the dealer and have them pull the part so you can inspect the flare and then you'll know for sure.

Thanks again, guys. Other than corrosion, the real issue is getting the new 6+ foot line burried inbetween the frame, harnesses, clamps, and oil pan rail. A brand new part would probably need to be bent a bunch to fit in in one piece, but with custom pipe I can install break halfway with a union if I desire. The cost savings is minor but still a bonus. As long as this uses double flares and readily available 3/8 pipe then I'm already set.

There's also the issue of the cooler, it appears to be an addon due to the constant towing this truck was set up for by the previous owner. It has a mix of barbed/clamped fittings and hose going to several locations behind the grille but I haven't looked closely or mapped it out. It's a bear to get on safety stands to inspect underneath. I already patched some leaking rustout with hose/clamps in a pinch and was saving the real repair for a slow day.

Thanks again, guys. Other than corrosion, the real issue is getting the new 6+ foot line burried inbetween the frame, harnesses, clamps, and oil pan rail. A brand new part would probably need to be bent a bunch to fit in in one piece, but with custom pipe I can install break halfway with a union if I desire. The cost savings is minor but still a bonus. As long as this uses double flares and readily available 3/8 pipe then I'm already set.....

Yeah, I hear you on that one. Sometimes the replacement lines aren't bent right anyway and it gets frustrating. Good luck!

Yeah, I hear you on that one. Sometimes the replacement lines aren't bent right anyway and it gets frustrating. Good luck!

Well, it's done, so here are the details for posterity. Mind you, I could have looked it over at some time before asking here, but I usually don't have access to it and it is a bear to lift and support safely so...

What I had remembered about the cooler appearing to be aftermarket was not accurate. Its hose had been cut and spliced once before me, then I cut and spliced another section, but as it turns out, this is an OEM cooler and lines/hoses, they just don't "look as OEM" as everything else on the truck.

I looked at the two pipes I wanted to replace (the ones that run along side the oil pan rail) and one of them was actually an assembly of two pipes and a hose with factory crimps. The other pipe "looked" like it just ended in a hose barb, but it had been shortened/repaired at least twice. So I checked out the parts availability from Ford since I decided it would be better to buy the complete assembly verses fashioning a hose section inbetween two pipes. The pipe assembly was only $39 list and the other pipe (which turns out really does have a simple hose barb on the radiator/cooler side) was only $23 list. It wasn't worth making pipes in this case so I bought them instead. The old tubing nuts were very tight but came out with clean threads with a little patience and mild rounding of the nuts.

For posterity (once again) there is a hose set from Ford that can be purchased for about $64 that goes from the pipe (returns ATF to trans at rear trans fitting) to the cooler in front of the radiator, then out of the cooler to a pipe that runs along the bottom of the radiator to the driver's side fitting. That pipe is not available anymore; Ford parts info indicates it must be fabricated in the field now. Unlike the pipes to the trans it didn't rust so I left it alone.

The original hose set on this truck had been extended with a barb, not cut, so I lucked out as this saved needing to fix or replace it. The rubber still seems to be in good shape even in the clamp area.

Oh, and yes, the fittings are 45* double flare and the tubing is 3/8" :-)

This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company.